/**
    * Copyright 2005-2012 The Kuali Foundation
    *
    * Licensed under the Educational Community License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.opensource.org/licenses/ecl2.php
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.kuali.rice.krms.framework.engine;
  
  import java.util.Collections;
  import java.util.List;
  
  import org.kuali.rice.krms.api.engine.ExecutionEnvironment;
  import org.kuali.rice.krms.api.engine.ResultEvent;
  import org.kuali.rice.krms.api.engine.Term;
  import org.kuali.rice.krms.api.engine.TermResolutionException;
  import org.kuali.rice.krms.framework.engine.expression.ComparisonOperator;
  import org.kuali.rice.krms.framework.engine.result.BasicResult;
  
  /**
   * An implementation of {@link Proposition} which uses a {@link ComparisonOperator} and {@link Term}
   * @param <T>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class ComparableTermBasedProposition<T> implements Proposition {
  	private static final ResultLogger LOG = ResultLogger.getInstance();
  
  	private final ComparisonOperator operator;
  	private final Term term;
  	private final T expectedValue;
  
      /**
       * Create a ComparableTermBasedProposition with the given values
       * @param operator {@link ComparisonOperator} to set the operator to
       * @param term {@link Term} to set the term to
       * @param expectedValue to set the expectedValue to
       */
  	public ComparableTermBasedProposition(ComparisonOperator operator, Term term, T expectedValue) {
  		this.operator = operator;
  		this.term = term;
  		this.expectedValue = expectedValue;
  	}
  
  	/**
  	 * @see org.kuali.rice.krms.framework.engine.Proposition#evaluate(org.kuali.rice.krms.api.engine.ExecutionEnvironment)
  	 * @throws TermResolutionException if there is a problem resolving the {@link Term}
  	 */
  	@Override
  	public PropositionResult evaluate(ExecutionEnvironment environment) {
  		Comparable<T> termValue;
  
  		termValue = environment.resolveTerm(term, this);
  
  		boolean result = compare(termValue);
  
  		if (LOG.isEnabled(environment)){
  			LOG.logResult(new BasicResult(ResultEvent.PROPOSITION_EVALUATED, this, environment, result));
  		}
  		return new PropositionResult(result);
  	}
  
  	/**
  	 * Compares the term value w/ the expected value
  	 *
  	 * @param termValue Comparable which makes up the {@link ComparisonOperator}.compare() left hand side object
  	 * @return the boolean result of the comparison
  	 */
  	protected boolean compare(Comparable<T> termValue) {
  		boolean result = Boolean.valueOf(operator.compare(termValue, getExpectedValue()));
  		return result;
  	}
  
      /**
       * Returns an empty list.  Collections.emptyList()
       *
       * {@inheritDoc}
       *
       * @return an empty list.  Collections.emptyList()
       */
    	@Override
  	public List<Proposition> getChildren() {
  	    return Collections.emptyList();
  	}
  	
  	@Override
  	public boolean isCompound() {
  	    return false;
  	}
  
  	/**
      * Returns the expectedValue
 	 * @return the expectedValue
 	 */
 	protected T getExpectedValue() {
 		return this.expectedValue;
 	}
 
     @Override
 	public String toString(){
 		StringBuilder sb = new StringBuilder();
 		sb.append(term.toString());
 		sb.append(" "+operator.toString());
 		sb.append(" "+expectedValue.toString());
 		return sb.toString();
 	}
 }